Sarah Chauncey Woolsey was an American childrens author who wrote under the pen name Susan Coolidge.

Woolsey was born January 29, 1835, into the wealthy, influential New England Dwight family in Cleveland, Ohio. Her father was John Mumford Woolsey (1796–1870) and mother was Jane Andrews. She spent much of her childhood in New Haven Connecticut after her family moved there in 1852.

Woolsey worked as a nurse during the American Civil War (1861–1865), after which she started to write. The niece of the author and poet Gamel Woolsey, she never married, and resided at her family home in Newport, Rhode Island, until her death.

She edited The Autobiography and Correspondence of Mrs. Delaney (1879) and The Diary and Letters of Frances Burney (1880). She is best known, however, for her classic childrens novel, What Katy Did (1872). The fictional Carr family was modeled after the authors own, with Katy Carr inspired by Susan (Sarah) herself, and the brothers and sisters modeled on Coolidges four younger Woolsey siblings.